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package org.openjdk.jmh.samples;


import org.openjdk.jmh.annotations.Benchmark;

import org.openjdk.jmh.annotations.BenchmarkMode;

import org.openjdk.jmh.annotations.Group;

import org.openjdk.jmh.annotations.GroupThreads;

import org.openjdk.jmh.annotations.Mode;

import org.openjdk.jmh.annotations.OutputTimeUnit;

import org.openjdk.jmh.annotations.Scope;

import org.openjdk.jmh.annotations.Setup;

import org.openjdk.jmh.annotations.State;

import org.openjdk.jmh.runner.Runner;

import org.openjdk.jmh.runner.RunnerException;

import org.openjdk.jmh.runner.options.Options;

import org.openjdk.jmh.runner.options.OptionsBuilder;


import java.util.concurrent.TimeUnit;

import java.util.concurrent.atomic.AtomicInteger;


@State(Scope.Group)

@BenchmarkMode(Mode.AverageTime)

@OutputTimeUnit(TimeUnit.NANOSECONDS)

public class JMHSample_15_Asymmetric {


 /*

  * So far all the tests were symmetric: the same code was executed in all the threads.

  * At times, you need the asymmetric test. JMH provides this with the notion of @Group,

  * which can bind several methods together, and all the threads are distributed among

  * the test methods.

  *

  * Each execution group contains of one or more threads. Each thread within a particular

  * execution group executes one of @Group-annotated @Benchmark methods. Multiple execution

  * groups may participate in the run. The total thread count in the run is rounded to the

  * execution group size, which will only allow the full execution groups.

  *

  * Note that two state scopes: Scope.Benchmark and Scope.Thread are not covering all

  * the use cases here -- you either share everything in the state, or share nothing.

  * To break this, we have the middle ground Scope.Group, which marks the state to be

  * shared within the execution group, but not among the execution groups.

  *

  * Putting this all together, the example below means:

  *  a) define the execution group "g", with 3 threads executing inc(), and 1 thread

  *     executing get(), 4 threads per group in total;

  *  b) if we run this test case with 4 threads, then we will have a single execution

  *     group. Generally, running with 4*N threads will create N execution groups, etc.;

  *  c) each execution group has one @State instance to share: that is, execution groups

  *     share the counter within the group, but not across the groups.

  */


 private AtomicInteger counter;


 @Setup

 public void up() {

  counter = new AtomicInteger();

 }


 @Benchmark

 @Group("g")

 @GroupThreads(3)

 public int inc() {

  return counter.incrementAndGet();

 }


 @Benchmark

 @Group("g")

 @GroupThreads(1)

 public int get() {

  return counter.get();

 }


 /*

  * ============================== HOW TO RUN THIS TEST: ====================================

  *

  * You will have the distinct metrics for inc() and get() from this run.

  *

  * You can run this test:

  *

  * a) Via the command line:

  *    $ mvn clean install

  *    $ java -jar target/benchmarks.jar JMHSample_15 -f 1

  *    (we requested single fork; there are also other options, see -h)

  *

  * b) Via the Java API:

  *    (see the JMH homepage for possible caveats when running from IDE:

  *      http://openjdk.java.net/projects/code-tools/jmh/)

  */


 public static void main(String[] args) throws RunnerException {

  Options opt = new OptionsBuilder()

          .include(JMHSample_15_Asymmetric.class.getSimpleName())

          .forks(1)

          .build();


  new Runner(opt).run();

 }

// 本例是对 @Group 和 @GroupThreads 使用的介绍，@Group 定义了一个线程组， @GroupThreads 可以分配线程给测试用例，可以测试线程执行不均衡的情况，比如三个线程写，一个线程读，这里用 @State(Scope.Group) 定义了counter 作用域是这个线程组。
}